This invention relates to an improved compound bow of the type employing cams and control cables to achieve a programmed draw weight that varies in a selected fashion as a function of draw length.
The invention is more particularly concerned with a compound bow in which the cam is interposed between an inboard spring limb member and an outboard rigid limb member.
A number of archery bows have been proposed in which programming means are incorporated to regulate the draw weight of the bow so that a maximum pull weight is attained at an intermediate draw position and a reduced draw weight is attained at full draw. These are typically referred to as compound bows. A number of these compound bows are described in U.S. Patent literature, namely Allen U.S. Pat. No. 3,486,495; Hofmeister U.S. Pat. No. 3,854,417; Trotter U.S. Pat. No. 3,923,035; Islas U.S. Pat. No. 3,981,290; and Islas U.S. Pat. No. 4,287,867.
The later patent, i.e., Pat. No. 4,287,867 describes a compound bow in which, on upper and lower ends of the riser, and outer rigid limb member is pivotally supported at its midsection on the outboard end of the cantilevered spring limb arm or power limb. A rotatable cam is pivotally supported on the riser, and a control cable which is received to the cam is connected at one end to the outer end of the spring limb arm and at the other end to the inboard end of the rigid limb member. The bowstring is strung between the outboard ends of the upper and lower rigid members. A synchronizing cable runs between upper and lower synchronizing wheels that turn with the rotatable cams.
Drawing the bow string rotates the outer limb member and flexes the spring limb arm. The control cable rotates the cam, and the profile of the cam programs the draw weight as a function of draw length. The draw weight varies non-linearly over the draw length and drops off somewhat at full draw, with full draw weight being achieved a short distance ahead of full draw.
While this compound bow design has proven to be quite successful, it has been desired to create a compound bow with still fewer parts, of lighter weight and smaller profile, and which has excellent draw weight characteristics.